1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Basic test for sigtrap support.
4 *
5 * Copyright (C) 2021, Google LLC.
6 */
7
8#include <errno.h>
9#include <stdint.h>
10#include <stdlib.h>
11#include <linux/hw_breakpoint.h>
12#include <linux/string.h>
13#include <pthread.h>
14#include <signal.h>
15#include <sys/ioctl.h>
16#include <sys/syscall.h>
17#include <unistd.h>
18
19#include "cloexec.h"
20#include "debug.h"
21#include "event.h"
22#include "tests.h"
23#include "../perf-sys.h"
24
25#define NUM_THREADS 5
26
27static struct {
28 int tids_want_signal; /* Which threads still want a signal. */
29 int signal_count; /* Sanity check number of signals received. */
30 volatile int iterate_on; /* Variable to set breakpoint on. */
31 siginfo_t first_siginfo; /* First observed siginfo_t. */
32} ctx;
33
34#define TEST_SIG_DATA (~(unsigned long)(&ctx.iterate_on))
35
36static struct perf_event_attr make_event_attr(void)
37{
38 struct perf_event_attr attr = {
39 .type = PERF_TYPE_BREAKPOINT,
40 .size = sizeof(attr),
41 .sample_period = 1,
42 .disabled = 1,
43 .bp_addr = (unsigned long)&ctx.iterate_on,
44 .bp_type = HW_BREAKPOINT_RW,
45 .bp_len = HW_BREAKPOINT_LEN_1,
46 .inherit = 1, /* Children inherit events ... */
47 .inherit_thread = 1, /* ... but only cloned with CLONE_THREAD. */
48 .remove_on_exec = 1, /* Required by sigtrap. */
49 .sigtrap = 1, /* Request synchronous SIGTRAP on event. */
50 .sig_data = TEST_SIG_DATA,
51 .exclude_kernel = 1, /* To allow */
52 .exclude_hv = 1, /* running as !root */
53 };
54 return attr;
55}
56
57#ifdef HAVE_BPF_SKEL
58#include <bpf/btf.h>
59
60static struct btf *btf;
61
62static bool btf__available(void)
63{
64 if (btf == NULL)
65 btf = btf__load_vmlinux_btf();
66
67 return btf != NULL;
68}
69
70static void btf__exit(void)
71{
72 btf__free(btf);
73 btf = NULL;
74}
75
76static const struct btf_member *__btf_type__find_member_by_name(int type_id, const char *member_name)
77{
78 const struct btf_type *t = btf__type_by_id(btf, type_id);
79 const struct btf_member *m;
80 int i;
81
82 for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
83 const char *current_member_name = btf__name_by_offset(btf, m->name_off);
84 if (!strcmp(current_member_name, member_name))
85 return m;
86 }
87
88 return NULL;
89}
90
91static bool attr_has_sigtrap(void)
92{
93 int id;
94
95 if (!btf__available()) {
96 /* should be an old kernel */
97 return false;
98 }
99
100 id = btf__find_by_name_kind(btf, "perf_event_attr", BTF_KIND_STRUCT);
101 if (id < 0)
102 return false;
103
104 return __btf_type__find_member_by_name(id, "sigtrap") != NULL;
105}
106
107static bool kernel_with_sleepable_spinlocks(void)
108{
109 const struct btf_member *member;
110 const struct btf_type *type;
111 const char *type_name;
112 int id;
113
114 if (!btf__available())
115 return false;
116
117 id = btf__find_by_name_kind(btf, "spinlock", BTF_KIND_STRUCT);
118 if (id < 0)
119 return false;
120
121 // Only RT has a "lock" member for "struct spinlock"
122 member = __btf_type__find_member_by_name(id, "lock");
123 if (member == NULL)
124 return false;
125
126 // But check its type as well
127 type = btf__type_by_id(btf, member->type);
128 if (!type || !btf_is_struct(type))
129 return false;
130
131 type_name = btf__name_by_offset(btf, type->name_off);
132 return type_name && !strcmp(type_name, "rt_mutex_base");
133}
134#else /* !HAVE_BPF_SKEL */
135static bool attr_has_sigtrap(void)
136{
137 struct perf_event_attr attr = {
138 .type = PERF_TYPE_SOFTWARE,
139 .config = PERF_COUNT_SW_DUMMY,
140 .size = sizeof(attr),
141 .remove_on_exec = 1, /* Required by sigtrap. */
142 .sigtrap = 1, /* Request synchronous SIGTRAP on event. */
143 };
144 int fd;
145 bool ret = false;
146
147 fd = sys_perf_event_open(attr: &attr, pid: 0, cpu: -1, group_fd: -1, flags: perf_event_open_cloexec_flag());
148 if (fd >= 0) {
149 ret = true;
150 close(fd);
151 }
152
153 return ret;
154}
155
156static bool kernel_with_sleepable_spinlocks(void)
157{
158 return false;
159}
160
161static void btf__exit(void)
162{
163}
164#endif /* HAVE_BPF_SKEL */
165
166static void
167sigtrap_handler(int signum __maybe_unused, siginfo_t *info, void *ucontext __maybe_unused)
168{
169 if (!__atomic_fetch_add(&ctx.signal_count, 1, __ATOMIC_RELAXED))
170 ctx.first_siginfo = *info;
171 __atomic_fetch_sub(&ctx.tids_want_signal, syscall(SYS_gettid), __ATOMIC_RELAXED);
172}
173
174static void *test_thread(void *arg)
175{
176 pthread_barrier_t *barrier = (pthread_barrier_t *)arg;
177 pid_t tid = syscall(SYS_gettid);
178 int i;
179
180 pthread_barrier_wait(barrier);
181
182 __atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
183 for (i = 0; i < ctx.iterate_on - 1; i++)
184 __atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
185
186 return NULL;
187}
188
189static int run_test_threads(pthread_t *threads, pthread_barrier_t *barrier)
190{
191 int i;
192
193 pthread_barrier_wait(barrier);
194 for (i = 0; i < NUM_THREADS; i++)
195 TEST_ASSERT_EQUAL("pthread_join() failed", pthread_join(threads[i], NULL), 0);
196
197 return TEST_OK;
198}
199
200static int run_stress_test(int fd, pthread_t *threads, pthread_barrier_t *barrier)
201{
202 int ret, expected_sigtraps;
203
204 ctx.iterate_on = 3000;
205
206 TEST_ASSERT_EQUAL("misfired signal?", ctx.signal_count, 0);
207 TEST_ASSERT_EQUAL("enable failed", ioctl(fd, PERF_EVENT_IOC_ENABLE, 0), 0);
208 ret = run_test_threads(threads, barrier);
209 TEST_ASSERT_EQUAL("disable failed", ioctl(fd, PERF_EVENT_IOC_DISABLE, 0), 0);
210
211 expected_sigtraps = NUM_THREADS * ctx.iterate_on;
212
213 if (ctx.signal_count < expected_sigtraps && kernel_with_sleepable_spinlocks()) {
214 pr_debug("Expected %d sigtraps, got %d, running on a kernel with sleepable spinlocks.\n",
215 expected_sigtraps, ctx.signal_count);
216 pr_debug("See https://lore.kernel.org/all/e368f2c848d77fbc8d259f44e2055fe469c219cf.camel@gmx.de/\n");
217 return TEST_SKIP;
218 } else
219 TEST_ASSERT_EQUAL("unexpected sigtraps", ctx.signal_count, expected_sigtraps);
220
221 TEST_ASSERT_EQUAL("missing signals or incorrectly delivered", ctx.tids_want_signal, 0);
222 TEST_ASSERT_VAL("unexpected si_addr", ctx.first_siginfo.si_addr == &ctx.iterate_on);
223#if 0 /* FIXME: enable when libc's signal.h has si_perf_{type,data} */
224 TEST_ASSERT_EQUAL("unexpected si_perf_type", ctx.first_siginfo.si_perf_type,
225 PERF_TYPE_BREAKPOINT);
226 TEST_ASSERT_EQUAL("unexpected si_perf_data", ctx.first_siginfo.si_perf_data,
227 TEST_SIG_DATA);
228#endif
229
230 return ret;
231}
232
233static int test__sigtrap(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
234{
235 struct perf_event_attr attr = make_event_attr();
236 struct sigaction action = {};
237 struct sigaction oldact;
238 pthread_t threads[NUM_THREADS];
239 pthread_barrier_t barrier;
240 char sbuf[STRERR_BUFSIZE];
241 int i, fd, ret = TEST_FAIL;
242
243 if (!BP_SIGNAL_IS_SUPPORTED) {
244 pr_debug("Test not supported on this architecture");
245 return TEST_SKIP;
246 }
247
248 pthread_barrier_init(&barrier, NULL, NUM_THREADS + 1);
249
250 action.sa_flags = SA_SIGINFO | SA_NODEFER;
251 action.sa_sigaction = sigtrap_handler;
252 sigemptyset(set: &action.sa_mask);
253 if (sigaction(SIGTRAP, &action, &oldact)) {
254 pr_debug("FAILED sigaction(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf)));
255 goto out;
256 }
257
258 fd = sys_perf_event_open(attr: &attr, pid: 0, cpu: -1, group_fd: -1, flags: perf_event_open_cloexec_flag());
259 if (fd < 0) {
260 if (attr_has_sigtrap()) {
261 pr_debug("FAILED sys_perf_event_open(): %s\n",
262 str_error_r(errno, sbuf, sizeof(sbuf)));
263 } else {
264 pr_debug("perf_event_attr doesn't have sigtrap\n");
265 ret = TEST_SKIP;
266 }
267 goto out_restore_sigaction;
268 }
269
270 for (i = 0; i < NUM_THREADS; i++) {
271 if (pthread_create(&threads[i], NULL, test_thread, &barrier)) {
272 pr_debug("FAILED pthread_create(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf)));
273 goto out_close_perf_event;
274 }
275 }
276
277 ret = run_stress_test(fd, threads, &barrier);
278
279out_close_perf_event:
280 close(fd);
281out_restore_sigaction:
282 sigaction(SIGTRAP, &oldact, NULL);
283out:
284 pthread_barrier_destroy(&barrier);
285 btf__exit();
286 return ret;
287}
288
289DEFINE_SUITE("Sigtrap", sigtrap);
290

source code of linux/tools/perf/tests/sigtrap.c